The main single difficulty which is encountered with irrigation emitters is the tendency for the emitters to block with insects, sand, mud, slime and decaying vegetable matter. In order for the emitter discharge to be slowed it is necessary to limit the size of an orifice or to incorporate a labyrinth conduit upstream of the orifice so that the flow rate is slow. In both instances, however, there is a tendency for blockage to occur due to deposition of solid or semi-solid particles, and although the cost of an emitter is small, the loss to a grower can be considerable since an emitter which fails to work but which is not readily identifiable can result in the loss of a valuable plant.
Various attempts are known to have been made in providing a self-cleaning facility within the design of an emitter, but as far as is known the difficulties which have been encountered heretofore have not been completely overcome and the attempts which have been made have not been persevered with.